Various devices are known for atomising a liquid. For example, the documents EP 0923957 and EP 1005916, both in the name of the present Applicant describe a liquid droplet spray device. A brief description of the liquid droplet spray device known from these documents, which are hereby incorporated by reference, is given here.
The spray device of the above-referenced documents consists of a housing formed of a superposition of a first substrate and a second substrate in-between which a space is formed for containing a liquid substance. One of the substrates contains outlet means containing outlet nozzles and output channels connecting these nozzles to the space. A liquid substance enters the spray device by way of, e.g., a very low pressure, e.g., around a few millibar or slightly negative pressure, or capillary action. This can be achieved for example by way of at least one input tube or needle through which the liquid substance may be supplied from an external reservoir into the spray device. The spray device further comprises a vibrating element, e.g. a piezoelectric element to cause vibration of the liquid substance in the space so as to cause the liquid to be ejected as a spray of droplets. There is no description of a system or of the arrangement of the external reservoir with respect to the device.
A liquid droplet spray system is known from the document U.S. Pat. No. 5,749,519. This device relates to an air freshener which has a reservoir for containing an air freshener liquid. The reservoir is connected to a vapour-emanating surface of a liquid dispensing device by way of a wick. The liquid is transmitted from the reservoir via the wick through capillary action to the vapour-emanating surface so as to dispense the air freshener.
Due to its design, and in particular due to the use of a wick, the liquid dispensing device always transmits the liquid to the vapour-emanating surface: Thus, to avoid waste and spill, the device is provided in a housing having a cover for sealing the vapour-emanating surface. Once the cover is removed, the vapour is dispensed into the surrounding air.
However, when the reservoir needs to be exchanged, the user will receive air freshener on his hands when manipulating the reservoir due to the wick being in contact with the liquid. Of course, air fresheners use strong fragrances so that this is not very pleasant. Further, this leads to a loss of liquid if one forgets to put the cover back on, and it is impossible to allow for a controlled dispersion of the vapour amount.
Another liquid droplet spray system is known from the document US 2002/0070239. This system has a reservoir, a flexible pouch, containing a porous material for absorbing the liquid of the reservoir. The reservoir is connected to a capillary channel, also containing a porous material, such as a wick. The channel leads the liquid to a perforated membrane surface. When the surface is vibrated by further provided vibration means, the liquid is dispensed as droplets.
Here again, a wick is used, both in the reservoir and in the capillary channel. Thus, when changing the reservoir, it would appear impossible to do such without any liquid spilling out.
Further, due to the design of the system, liquid may leak through the perforated membrane even when the system is not in use thus leading to wastage and related inconveniences such as unwanted fragrancing. Of course, controlled dispensing is not possible either with this system.
Another droplet spray device is known from the document U.S. Pat. No. 6,062,212 which describes a liquid dispenser having vibration means which are activated to expel liquid from a mesh in the usual manner, but which remain activated to ensure a complete emptying of the liquid from the dispenser. The disadvantage is that this additional atomising duration will sometimes be either too long or too short and that a fixed time will not work with liquids of various viscosities and surface tensions and ambient conditions.
Another droplet spray device is known from co-pending application no. EP 04 001 566.1 in the name of the present Applicant. This device consists of a disposable part having a reservoir for containing a liquid substance, and a valve for blocking the reservoir so as to avoid spill when the device is not in use, and a permanent, non-disposable part having the nozzle body, a piezo-electric actuator, electronic control means, and a fluidic interface linking the reservoir to the space in the nozzle body. Although this device overcomes many of the above-raised inconveniences due to partly disposable items, it suffers from contamination of the space of the droplet spray device, which may in certain cases not be fully emptied after use. A re-fill with another liquid substance will thus result in uncontrolled release, either in quantity or in actual substance caused by contamination.
Further, due to the presence of any remaining liquid substance, clogging may occur of the fluidic channel, of nozzles in the nozzle body or even of the reservoir thus impeaching the operation of the device.
It is, therefore, an object of the present invention to provide a liquid droplet spray system that overcomes the above-mentioned inconveniences and that can be efficiently used for liquid substances such as perfumes or other non-aqueous solvent based liquids, or for liquid medicaments.
It is another object of the present invention to provide such a system that is simple, reliable and inexpensive to manufacture, small in size and low in energy consumption and cost, and as such suitable as a personal or ambient fragrance and functional liquid dispenser.